The present invention relates to a tape measure provided with an end hook member attached to the free end of the measuring tape.
A tape measure provided with an end hook slidably riveted to the free end of the measuring tape, which end-hook can move with a stroke equal to its thickness along the measuring tape is known. When measuring an outer size of an object, the user hooks the end hook of the tape measure by an inside surface of its catch portion onto the external surface of a thing to be measured and extend measuring tape to the point of measurement. At this time, the end hook moves from the end of the measuring tape until the inside surface of the catch of the end hook is brought into coincidence with a zero point of a scale printed on the measuring tape. When measuring an inner size of an object, the end of the end hook is abutted against the object and, in this case, the end hook moves toward the end of the measuring tape until the front surface of the catch of the end hook is brought into coincidence with the zero mark of the scale printed on the measuring tape.
With the tape measure having the slidable end hook, the zero point of measurement for measuring inner size and outer size of the object is automatically set by movement of the end-hook relative to the end of the measuring tape. In other words, the tape measure eliminates a possible error of the measurement due to the thickness of the catch portion of the end hook.
In the above-mentioned tape measure, the measuring tape is wound on a winding reel provided with a spiral spring therein. The tape measure is usually used by manually extending the measuring tape from the housing against the returning force of the spring when measuring a size of an object and by automatically retracting the measuring tape into the housing by the accumulated returning power of the spring after measurement. The returning movement of the tape is stopped when the end hook strikes the housing. The collision of the end hook with the housing transmits a shock from the hook through the fastening rivets to the measuring tape. After repeated collisions the tape at the rivets may break. Some solutions to solve the above-mentioned problems have been proposed, for example, by Japanese Laid-open Utility Model Publication Nos. 2-115102 and 7-41401 and U.S. Pat. No. 5,659,970.
Recently, there has been a remarkable need for tape measures having wider and longer measuring tapes that must be provided with power return springs having a larger recoiling power. The large measuring tapes, however, involve an increased risk of breakage of the end of the measuring tape because rewinding the extended tape by the increased force of the spring may cause an accelerated movement of an increased mass of the tape and, therefore, the collision of the end hook with the housing may transmit a heavy shock to the tape end that may be broken.
The conventional tape measure has an end hook whose radius of curvature is the same as the measuring tape has. This may introduce an error of inside dimension measurement because the end of the measuring tape may stop at a bend formed between the shank portion and catch portion of the hook, resulting in incorrect zero setting when abutting the catch portion against a reference surface of an object for inside dimension measurement. Furthermore, the end hook may be subjected to cracking in material and/or corrugation thereof at the bend portion in the process of draw forming of the end hook.
The conventional tape measures involve such a problem that a scale figure put on the free end of the measuring tape may be hidden behind the shank portion of the end hook. The shank portion of the end hook is narrow and does not allow making a viewing port therein.